The High-Definition Multimedia Interface (HDMI®) has become the prevailing interface standard for transmitting digital video and audio data from high bandwidth audiovisual (AV) source devices to display devices. Examples of AV source devices include Blu-ray Disc and High Definition Digital Versatile Disc players. Examples of AV display devices include video projectors, digital televisions, and surround sound receivers. Certain AV source devices provide audio signals for surround sound, which is a method for improving the quality of sound reproduction. Surround sound systems include audio channels for speakers that surround the listener to the sides and rear, in addition to center, left, and right channels (the “screen channels”), which are intended for speakers arranged in the listener's forward direction.
In a typical surround sound system, the screen channels are connected to speakers that are integrated in a digital television and/or speakers installed as in-wall architectural units. Of the screen channels, the center channel is the most important, because it conveys the sound that corresponds to the action being displayed in the television picture. For example, the dialog that accompanies a television picture is critical to understanding the action and story, and it is typically carried on the center channel.
In spite of its importance to audiovisual presentations, the center channel signal in a home theater system is generally played on a speaker selected not on the basis of optimal sound quality, but on the basis of the space available and the aesthetic concerns of the homeowner. In instances where a dedicated center channel speaker is not practical, for example when installing a large flat-panel television over a fireplace, the standard practice of the home theater industry has been to direct the center channel audio identically to the left and right speakers, a technique known as creating a phantom center.
The phantom center technique defeats the stereophonic separation of the left and right channels and makes the dialog less intelligible. It also destroys the movement of sound (called “panning”) from side through center to side, which is essential to the surround sound experience. With the increasing use of large flat panel televisions as part of surround sound systems, more and more listeners settle for the degraded quality of phantom center sound because it is impractical to install a dedicated center channel speaker. For the foregoing reasons, there is a need for an apparatus that improves the quality of stereophonic sound in surround sound systems that lack a dedicated center channel speaker.